[pango/gi-docs: 25/74] docs: Convert fonts section to pango_fonts.md

[Matthias Clasen <matthiasc src gnome org>]

commit 129ebcdc70053f71f6a5cefb00623d7b89189cfa
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Feb 17 01:10:38 2021 -0500

    docs: Convert fonts section to pango_fonts.md

 docs/meson.build    |  1 +
 docs/pango.toml.in  |  1 +
 docs/pango_fonts.md | 65 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 pango/fonts.c       | 13 -----------
 4 files changed, 67 insertions(+), 13 deletions(-)
---
diff --git a/docs/meson.build b/docs/meson.build
index 4e2c06e8..fdf49162 100644
--- a/docs/meson.build
+++ b/docs/meson.build
@@ -3,6 +3,7 @@ gidocgen = find_program('gi-docgen', required: get_option('gtk_doc'))
 pango_content_files = [
   'pango_rendering.md',
   'pango_markup.md',
+  'pango_fonts.md',
   'pango-name.png',
   'layout.png',
   'pipeline.png',
diff --git a/docs/pango.toml.in b/docs/pango.toml.in
index 1e8c0048..eca52ea2 100644
--- a/docs/pango.toml.in
+++ b/docs/pango.toml.in
@@ -57,6 +57,7 @@ base_url = "https://gitlab.gnome.org/GNOME/pango/-/blob/master/";
 content_files = [
   "pango_rendering.md",
   "pango_markup.md",
+  "pango_fonts.md",
 ]
 
 content_images = [
diff --git a/docs/pango_fonts.md b/docs/pango_fonts.md
new file mode 100644
index 00000000..6e28e8f7
--- /dev/null
+++ b/docs/pango_fonts.md
@@ -0,0 +1,65 @@
+---
+Title: Fonts and Glyphs
+---
+
+# Fonts
+
+Pango supports a flexible architecture where a particular rendering architecture
+can supply an implementation of fonts. The `PangoFont` structure represents an
+abstract rendering-system-independent font. Pango provides routines to list
+available fonts, and to load a font matching a given description.
+
+Conceptually, Pango groups fonts into faces and families which are identified
+by a name. A *font face* provides the different sizes of a single font style.
+A *font family* provides the available styles of a font.
+
+As an example, "Helvetica" is a family, "Helvetica Bold" is a face of this
+family, and "Helvetica Bold 12pt" is a concrete font of this face.
+
+# Font Enumeration
+
+The central object for dealing with the available fonts on a system and caching
+loaded fonts is a [class@Pango.FontMap]. An application typically uses a single
+font map.
+
+Since the font map depends on the rendering architecture in use, you'll need to
+use the backend function pango_cairo_font_map_get_default() to obtain the default
+fontmap. Depending on the platform, it will return a `PangoCairoFcFontMap`, a
+`PangoCairoWin32FontMap` or a `PangoCairoCoreTextFontMap`.
+
+Once you have a fontmap, you can enumerate the available font families with
+[method@Pango.FontMap.list_families]. To enumerate the faces of a font family,
+use [method@Pango.FontFamily.list_faces].
+
+# Font Descriptions
+
+Since loading fonts uses system resources, Pango provides a way to describe
+a font without loading it. A [struct@Pango.FontDescription] is a struct that
+contains enough information to load a concrete font with
+[method@Pango.FontMap.load_font] or [method@Pango.Context.load_font]. You can
+obtain a font description from a font face using [method@Pango.FontFace.describe],
+or by parsing a string such as
+
+    Helvetica Bold 12pt
+
+with [method@Pango.FontDescription.from_string].
+
+# Glyphs
+
+A font provides information about glyphs and how to position and render them.
+The Pango rendering pipeline uses this information to create a
+[struct@Pango.GlyphString], which contains the glyphs corresponding to the
+characters in the text and related information such as glyph positions and sizes,
+and clustering information (i.e. which glyphs correspond to which characters).
+
+![A glyph string](rects3.png)
+
+A glyph is identified by a [alias@Pango.Glyph], which is a numeric ID. Note that
+glyph IDs are font-specific: the same character can be represented by diffferent
+glyph IDs in different fonts.
+
+The mapping between characters and glyphs is in general neither 1-1 nor a map:
+a single glyph may represent multiple characters (as is the case with ligatures),
+a single character may be represented by multiple glyphs (for example, when
+combining accents and base character), and in complex scripts, multiple characters
+may form clusters that get rearranged and represented by multiple glyphs.
diff --git a/pango/fonts.c b/pango/fonts.c
index a778facd..3ee21b0c 100644
--- a/pango/fonts.c
+++ b/pango/fonts.c
@@ -19,19 +19,6 @@
  * Boston, MA 02111-1307, USA.
  */
 
-/**
- * SECTION:pangofont
- * @short_description:Structures representing abstract fonts
- * @title: Fonts
- *
- * Pango supports a flexible architecture where a
- * particular rendering architecture can supply an
- * implementation of fonts. The #PangoFont structure
- * represents an abstract rendering-system-independent font.
- * Pango provides routines to list available fonts, and
- * to load a font matching a given description.
- */
-
 #include "config.h"
 #include <stdlib.h>
 #include <math.h>